The present invention relates in general to electronic equipment and a method for enabling at least two types of batteries to be selectively used, and more particularly to electronic equipment, such as a portable radio apparatus, which is capable of carrying out the indication of a remaining power of a battery, the warning about a low power of a battery, the control for limitation of the operation, and the like.
The description will hereinafter be given with respect to conventional electronic equipment, which carries out the indication of a remaining power of a battery as a power source, the warning about a low power of a battery, the control for limitation of the operation, and the like on the basis of comparison of an output voltage of the battery with the discharge characteristic data of the battery, which is previously specified, with reference to FIG. 3. FIG. 3 shows a typical example of a configuration of a conventional portable radio apparatus.
A radio apparatus 1 includes: a transmission/reception unit 2 for carrying out transmission/reception; resistors 3 and 4 for dividing a power source voltage; an A/D conversion unit 5 for subjecting the divided power source voltage to A/D conversion; a memory unit 7 for storing data relating to discharge characteristics or data relating to a voltage range for display of a remaining power of a battery 10 integrated into the radio apparatus 1; a microcomputer 6 for controlling the transmission/reception unit 2 and driving a display unit 8 for indicating a state of the power source voltage on the basis of both the discharge characteristic data which is stored in the memory unit 7 and the data relating to the power source voltage which is obtained by the A/D conversion in the A/D conversion unit 5; and a regulated power source unit 9 for stabilizing the voltage of the battery 10 which varies with time in order to supply those units with the electric power. The battery 10 is integrated into the radio apparatus 1 configured described above so as to supply those units with the electronic power.
Next, the description will hereinbelow be given with respect to the operation of carrying out the indication of a remaining power of the battery, the warning about a low power of the battery, the control for limitation of the operation on the basis of comparison of the output voltage of the battery integrated into the radio apparatus 1 with the discharge characteristic data of the battery which is previously specified.
In FIG. 3, the discharge characteristic data or the data relating to the voltage range for indication of a remaining power of one type of battery for use in the radio apparatus is previously stored in the memory unit 7. Now, the discharge characteristic data is, as shown in FIG. 4, meant data 20 expressed by the characteristic curve exhibiting the relationship between the discharge time and the battery voltage. In addition, the voltage range for indication of a remaining power is meant a voltage range ranging from a full charging voltage to a discharge end voltage.
The power source voltage of the battery 10 is divided by the resistors 3 and 4 and is subjected to the A/D conversion in the A/D conversion unit 5 to be supplied to the microcomputer 6.
The microcomputer 6 converts the voltage data outputted from the A/D conversion unit 5 into power source voltage data, compares the power source voltage data obtained by the conversion with the discharge characteristic data of the battery 10, shown in FIG. 4, which is stored in the memory unit 7, and detects which point on the discharge characteristic curve the power source voltage is located. Then, the microcomputer 6 calculates the remaining power of the battery on the basis of the detection result, and instructs the display unit 8 to indicate the data relating to the remaining power of the battery in the form of a percentage display or a bar chart. Then, the user can recognize the degree of consumption of the battery power by looking at that display.
As for the method of calculating the remaining power of the battery, heretofore, some methods have been well known. For example, there is well known a method wherein the discharge amount of battery is obtained by carrying out the integral calculation on the basis of both the data relating to the power source voltage, which varies with time, from the A/D conversion unit 5 and the discharge characteristic data shown in FIG. 4, and hence the remaining power of the battery can be calculated at the ratio of the discharge amount of the battery thus calculated to the total capacity of the battery.
As for the method of calculating the remaining power of the battery, there is well known another method wherein the discharge time ranging from the full charging voltage in which the remaining power of the battery is 100% to the discharge end voltage in which the remaining power of the battery is 0% is divided into five equal parts as shown in FIG. 5, the data relating to the discharge time periods of the resultant five equal parts is stored in the memory unit 7, the discharge time period when the radio apparatus 1 is actually used is timed, and the discharge time period thus timed is compared with the discharge time parts the data of which is stored in the memory unit 7, whereby the data relating to the remaining power of the battery can be displayed with the five equal parts. Incidentally, the number of division parts may be selected arbitrarily.
At the time when detecting that the output voltage of the battery 10 is decreased to a level equal to or lower than a predetermined value, the microcomputer 6 generates, in addition to the display of the remaining power of the battery, for example, an alarm sound or a warning indication for a low power of the battery in order to urge the user to charge the battery 10. In addition, at the time when detecting that the output voltage of the battery 10 is decreased to reach the discharge end voltage of the battery 10, the microcomputer 6 carries out the control in such a way as to turn off the power source of the transmission/reception unit 2, thereby preventing the battery 10 from being excessively discharged.
The alarm sound for the low power of the battery is generated at a time point when the output voltage of the battery 10 reaches a voltage value which is slightly larger than the discharge end voltage. As a result, the over discharge of the battery can be prevented and also the inconvenience for utilization can be prevented in which the output voltage of the battery 10 reaches the discharge end voltage and the power source of the electronic apparatus is unexpectedly turned off.
As for such a battery integrated into the electronic equipment configured as described above, the various batteries are present in correspondence to the continuous operating time, the weight, the price, the size, and the like of the electronic equipment having the associated battery integrated thereinto. In the conventional electronic equipment, however, it is impossible to identify the type and the capacity of the battery integrated thereinto, and hence only the specified one type of battery can be used.
More specifically, in the conventional electronic equipment, the discharge characteristic data and the data relating to the voltage range for display of the remaining power of the battery having the specified type and capacity are stored in the memory unit. Then, if the battery having the type and capacity different from those specified are used, then the following inconvenience will occur.
(1) The deviation occurs in the display of the remaining power of the battery, and hence the user can not confirm the degree of consumption of the power of the battery being used. PA1 (2) In the case where the data of the reference voltage and the discharge end voltage which is stored in the memory unit 7 and is used in order to generate the alarm sound for the low power of the battery is highly deviated with respect to the characteristics of the battery integrated into the electronic equipment, the user is urged to charge the battery though the battery is sufficiently discharged. In particular, in the nickel series secondary battery and the like, the phenomenon in which when the insufficient charge/discharge is repeated, the power source voltage or the capacity is apparently reduced, i.e., the so-called memory effect is caused. PA1 (3) In the case where the data of the reference voltage and the discharge end voltage which is stored in the memory unit 7 and is used in order to generate the alarm sound for the low power of the battery is lowly deviated with respect to the characteristics of the battery integrated into the electronic equipment, there is an evil that the over discharge of the battery is caused and hence the lifetime of the battery is shortened. In particular, in the lithium series secondary battery and the like, there is a risk of causing the explosion.
In addition, since the discharge characteristics of the battery varies depending on the temperature of the battery, in the specified battery as well, the change in the temperature of the battery due to the ambient temperature of the electronic equipment in use, the calorification of the electronic equipment, and the like results in the above-mentioned inconvenience in utilization being caused.
This will hereinbelow be concretely described with reference to FIG. 8. FIG. 8 shows the discharge temperature characteristics when a Ni-Cd series battery with 600 mAh rated capacity is discharged with a constant current as the discharge current of 600 mA. As apparent from FIG. 8, the voltage of the battery is soon dropped as the ambient temperature is lower with the discharge capacity at a room temperature (23.degree. C.) as 100%. In this connection, if the voltage value of this battery for the warning about the low power of the battery is 10.8V and the battery is discharged with a constant current of 600 mA, though the battery is not sufficiently discharged at -20.degree. C., a user urged to charge the battery. This results in that the operating time of the electronic equipment is extremely shortened and the memory effect is caused.
In addition, in the case where the current consumption of the electronic equipment having a battery as its power source is greatly changed, e.g., as in the portable radio apparatus, the current consumption is largely changed depending on the operation mode such as transmission, reception and a waiting mode, since a large current is caused to flow in transmission so that the voltage is developed across the internal resistance of the battery, the errors occur in the indication of the remaining power of the battery and the warning about the low power of the battery and hence the convenience of using the battery is very poor. This is a big problem.
This problem will hereinbelow be described more concretely with reference to FIG. 9. FIG. 9 shows the discharge temperature characteristics of a lithium ion series battery in the actual use state of the radio apparatus. As apparent from FIG. 9, if a large current of 1,300 mA for example is caused to flow in the transmission state, then the large voltage is developed across the internal resistance of the battery. In this connection, if the battery is discharged with 9.5V as the voltage value for warning about the low power of the battery, though the remaining power is still available in both the reception mode and the waiting mode and hence the battery can be used, since in the transmission mode, the warning about the low power of the battery is issued due to that voltage drop across the internal resistance of the battery, a user is urged a little early to charge the battery and hence the accurate judgement can not be obtained. Further, since the internal resistance of the battery increases and hence the voltage drop thereacross becomes large as the ambient temperature is lower, this results in the above-mentioned inconvenience being increased.
In addition, in the electronic equipment, such as a portable radio apparatus, which operates with such a battery, it is desirable that the malfunction of the load equipment and the destruction of the battery resulting from the reduction of the terminal voltage of the battery can be prevented and also the prolongation of the operating time which is provided by the battery can be obtained as much as possible.
Conventionally, in addition to the above-mentioned voltage threshold for the warning about the low power of the battery, the threshold for the discharge end detection voltage of the battery is previously set to a level lower than that threshold. Then, at the time when the terminal voltage of the battery is decreased down to the discharge end detection voltage, the remaining power of the battery is regarded as zero, and then the operation of the electronic equipment is stopped.
In the above-mentioned prior art, there arises a problem that it is not said that the accurate detection of the remaining power of the battery is suitably taken into consideration, and hence the dissatisfaction still remains with respect to the sufficient utilization of the battery capacity.
That is, while the terminal voltage of the battery is certain a factor representing the remaining power of the battery, the terminal voltage is also changed due to any other factor and hence does not necessarily correspond to the remaining power of the battery uniquely.
In the prior art, however, as described above, since the remaining power of the battery is simply judged on the basis of only the terminal voltage of the battery, this lacks in accuracy.
This problem will hereinbelow be described more concretely with reference to FIG. 10.
Firstly, FIG. 10 shows the voltage characteristics when a lithium ion secondary battery in which a terminal voltage V.sub.B in the charge state is 12.6V (4.times.3 cells) and the rated capacity recommendation value is about 800 mAh is used with the recommendation rated current (e,g., 150 mA). In this case, there is shown the characteristics that due to the change in the internal resistance resulting from mainly the discharge of the battery, as shown in the figure, the terminal voltage decreases with the progress of the discharge. Incidentally, it is well known that in the case of the lithium ion series secondary battery, the change in the internal resistance is particularly remarkable.
Now, in this case, if the discharge end detection voltage is set to 8.1V as shown in the figure, and firstly, the remaining power of the battery is detected under the rated current, then it is detected in a point 1 that the remaining power of the battery is zero. In this case, the battery can be utilized up to approximately the rated capacity.
However, when the electronic equipment which is powered by this battery is a portable radio apparatus or the like in which the current is greatly changed during the use thereof, e.g., the power consumption in transmission is largely different from the power consumption in reception, the large current such as 1,300 mA is caused to flow in transmission. At this time, as shown in the figure, the large voltage drop is developed due to the internal resistance of the battery.
For this reason, at this time, as illustrated by a point 2, though only about 700 mAh is discharged yet, it will be judged at this point that the remaining power of the battery is zero, and hence the accurate judgement for the remaining power of the battery can not be obtained.
Further, in addition thereto, in the above-mentioned conventional electronic equipment, terminals used to detect the type of the battery and the various batteries having different capacities, i.e., terminals used to detect the type and capacity of the battery are required to be provided for both the electronic equipment side and the battery side. Mounting the terminals to both the electronic equipment and the battery results in that the additional physical volume is required therefor, and the structure becomes complicated in order to ensure the stability such as the connection of the terminals to reduce the producibility. In other words, such mounting is disadvantageous in terms of miniaturization, lightness and the cost of the electronic equipment. Further, in the equipment for which waterproof and the like are required, the realization of the equipment per se becomes difficult due to the complicatedness in its structure.